How to Repair a Corrupt XLSX FileDeveloped by Microsoft and included in its Office suite of productivity products, Excel is one of the world's most widely used spreadsheet applications, as of October 2010. With the release of Excel 2007, the program began saving spreadsheets in the XML-based XLSX format by default. If the content of an XLSX file becomes corrupted, Excel generally starts an automatic recovery process that attempts to repair the data. Should this fail to happen, initiate the process yourself with just a few clicks.